The present invention relates generally to coagulants for water treatment applications. In general, coagulants are utilized to remove suspended solid particles from aqueous systems.
Coagulants typically fall into the general category of inorganic (trivalent, divalent metal salts) or organic (water soluble polyelectrolytes). Examples of widely used inorganic coagulants are aluminum sulfate Al.sub.2 (SO.sub.4).sub.3, aluminum chloride AlCl.sub.3, aluminum chlorohydrate Al.sub.2 (OH).sub.5 Cl, ferric chloride FeCl.sub.3, ferric sulfate Fe.sub.2 (So.sub.4).sub.3, and calcium chloride. Examples of commonly used water soluble or solution polyelectrolytes are p-DMDAAC (polydimethyl diallyl ammonium chloride) and Epi-DMA polyamine Epichlorohydrin-dimethylamine).
Many inorganic coagulants are compatible with solution cationic polyelectrolytes and can be combined to form stable combinations. In recent years, many different blend formulations of an inorganic coagulant with a high charge solution cationic polyelectrolyte have been patented and marketed. An example of an inorganic coagulant/polymer blend might be: 5 parts of a standard 280 Baume AlCl.sub.3 solution mixed with 1 part of Epi-DMA polyamine. More examples, limits, and ranges are explained in U.S. Pat. Nos. 4,746,457, 4,900,019, and 5,035,808 to Calgon Corporation, and further in U.S. Pat. Nos. 2,862,880, 3,285,849, 3,472,767, 3,489,681, 3,617,569, 4,137,165, 4,450,092, 4,582,627, 4,610,801, and 4,655,934, the disclosures of which are incorporated herein by reference in their entirety. Normally, these compositions are physical blends of an inorganic trivalent metal salt solution and a water soluble polymer solution, which is a simple mixture of the components where both components retain their original identity or chemical composition, but provide utility and advantages such as:
1. a synergy of adding the inorganic and polymeric coagulants simultaneously as a blend; and PA1 2. ease of use--using one product instead of two (thereby eliminating feed systems, equipment, and handling).
Wastewater treatment systems typically require the use of trivalent metal salts, a polymer or a combination of both in the coagulation process. Both ferric coagulants such as FeCl.sub.3 blends and aluminum coagulants such as alum or Al.sub.2 (OH).sub.5 Cl blends are often used for these processes. Both the ferric and aluminum coagulants provide different desirable properties. However, these coagulants are normally incompatible with each other.
It was thus desired in the art to develop a single coagulant which would combine the desirable properties of ferric and aluminum coagulants.